DALLAS -- A former walk-on measuring all of 5-fot-10, 180 pounds might have the signature play of the College Football Playoff era. Not that Clemson receiver Hunter Renfrow cares much at this point.

"The playoff wasn't even a thing when I was in high school," said the Tigers redshirt senior slot receiver.

Renfrow has been at Clemson as long as the CFP has been in existence (five years). That makes him somewhat of an authority on Clemson, the CFP and the implications of another championship chase.

Renfrow remains the CFP's leading receiver with 32 catches in five games. He still basks in the glow created by his game-winning catch to beat Alabama two years ago for Clemson's first national championship in 35 years.

"That play just represents so much," Renfrow said. "That was kind of how we wanted to finish."

Now, for the new reality at Clemson. Never mind the Tigers are undefeated in the regular season for the second time in the last four years. Never mind Clemson has been ranked second behind No. 1 Alabama in nine of the season's 14 weeks, never dropping below No. 3.

That is what the Tigers are supposed to do.

The only way this season ends right (for Clemson fans) is a CFP National Championship win over Alabama.

But there's one problem for No. 2 Clemson: No. 3 Notre Dame is in the way in this Cotton Bowl semifinal.

The Irish are similarly undefeated. Like the Tigers, they changed quarterbacks a month into the season and got … better. Their history is decades longer than most everyone.

But how that helps them Saturday afternoon is to be determined. The Irish are not only an underdog, considering the 12 ½-point spread (as of Thursday), they are an epic underdog as that's the biggest postseason point-spread deficit ND has faced in at least 41 years. In the first four years of the CFP, the winning team has covered in each of the eight semifinal games.

"Notre Dame is nothing to be laughed at," Clemson linebacker Tre Lamar said. "They're undefeated, too. We've watched all their games. We have to make sure we sell out [emotionally] for this game or we won't make it to the next one."

The Tigers keep telling themselves that. They and the Crimson Tide have become the most prominent rivalry of the playoff era, the Yankees-Red Sox of the last half decade. Before that, Clemson was building itself into a power under coach Dabo Swinney. Alabama was already there many times over under Nick Saban.

But the Tigers are close, real close.

Since January 2016, the teams have met three times in the CFP. Alabama has won two. Renfrow's catch with one second left two years ago in Tampa, Florida, got the Tigers their only win.

Wins by the Tide and Tigers on Saturday would clinch a fourth straight meeting. If Renfrow has the signature play of the CFP era, that makes Clemson and Alabama the CFP's featured performers these five years of its existence.

The Tigers have played in three straight playoffs. Only Alabama (with appearances in all four CFPs) has played more. Clemson has played in six total playoff games (winning four). Only Alabama has played more (seven, winning six).

"I would say we've been here so many times we're just really ready," Lamar said.

And primed. Clemson's defensive line is one of the best ever. Its true freshman quarterback, Trevor Lawrence, was the No. 1 recruit in the Class of 2018. In one recent mock draft, Clemson had five players projected to go in the first round. Notre Dame had six players projected to be drafted.

"Certainly people have [favored Clemson] outside our locker room," Irish linebacker Drue Tranquill said. "We have a deep belief in yourself."

If Renfrow is the old man of the CFP, Clemson's CFP appearances have become so common one media member asked coach Dabo Swinney if the postseason has become "old hat."

"Every day, I have a moment," Swinney said. "Every day, I get to walk on this field. Every day, I get to hop on the [team] bus and watch those crazy people on those police motorcycles. … I just appreciate every aspect of it to the nth degree."

To dismiss Notre Dame is to dismiss all those years of tradition and excellence. More in the moment, Ian Book is the only quarterback among the semifinalists to have at least two touchdown passes in each start. That, at least, is a beginning.

"I feel like Notre Dame has a same type of edge that we have because it's they're first time being in it," said Clemson defensive lineman Clelin Ferrell. "It's a once-in-a-lifetime chance; you're not guaranteed to come to this playoff every year."

Alabama and Clemson come pretty close.